Research On Non-synchronized Section Location Technology Of Single-phase Ground Fault In Grounding System

When a single-phase ground fault occurs in a small-current grounded distribution system,the current signal changes little and the amplitude of the transient information is small.Therefore,fault line selection and section location based on power frequency steady state and transient signals have misjudgments.Therefore,fault location based on transient signals has become a hot spot for researchers.At the same time,this paper considers the accuracy of the zero sequence current data used by the positioning technology.Starting from the synchronization of the three-phase current data,the three-phase current is accurately synchronized.The positioning technology of the fault section is further studied.The data synchronization method based on Drosophila optimization algorithm,the segment positioning method based on amplitude frequency characteristics and similarity calculation,and the segment positioning method based on HAUSDORFF distance comparison have achieved the following results:1)Aiming at the problem of data synchronization in the distributed multi-point measurement system of the distribution network,in order to accurately extract the zero-sequence current required for section positioning,a steady-state information before failure based on fruit fly optimization algorithm is proposed to correct the transient state after failure Information data synchronization technology.Firstly,the zero-sequence characteristics of the three-phase current are analyzed,combined with the zero-sequence current characteristics,a synchronous start criterion is constructed to start fine synchronization.In fine synchronization,the three-phase current synchronization error is controlled within one cycle according to the wavelet algorithm.Furthermore,using the characteristics of the steady-state phase current function before the fault to construct its trigonometric function,and then using the zero-sequence feature to establish the optimal model,that is,the objective function,combined with the fruit fly optimization algorithm to solve the objective model to obtain the synchronization error.2)Aiming at the difference in frequency domain characteristics of the upstream and downstream transient information in the fault section of the small current distribution system,a section positioning method based on the improved correlation coefficient method is proposed.Based on S transform to realize the amplitude-frequency information analysis of the zero-sequence current,and analyze the problem of the blind zone of the fault section in the traditional correlation coefficient method;further analysis of the upstream anddownstream zero-sequence current main resonant frequency and non-main resonant frequency(generated by the distributed parameters of the line)Information difference,it is proposed to expand the S-transform to analyze the zero-sequence current frequency domain to improve the correlation coefficient calculation.By comparing the correlation coefficient of the upstream and downstream frequency domain information with the threshold,the location of the segment is realized and the influence of the blind zone is reduced.3)Aiming at the difference of the full-band amplitude characteristics of the upstream and downstream transient information in the fault section of the small current distribution system,a fault section location method based on the Hausdorff distance algorithm is proposed.Construct a resonant distribution network system to clarify the fault characteristics of the zero-sequence current transient components,analyze the problems of the traditional correlation coefficient method for segment positioning.In this paper,wavelet decomposition is used to reconstruct the zero-sequence current transient components,and calculate the sound and fault segments.Downstream zero-sequence current transient component amplitude ratio,and introduce Hausdorff distance algorithm to measure the upstream and downstream zero-sequence current transient component amplitude characteristic matching degree of feeder section,and further distinguish the fault section by comparing with the set threshold.Based on PSCAD/EMTDC,a simulation model of the distribution network hybrid line was built to verify the research content of this paper: the recording data synchronization method based on the fruit fly optimization algorithm provides accurate and reliable zero-sequence current;the proposed section positioning method There is no dead zone for positioning,and the fault section can be accurately located under multiple types of grounding methods.